Cells are cultivated with a culture vessel such as a dish or a petri dish into which a culture solution is poured. Then, when an incubation time elapses, the culture vessel may be filled with the cells or it may be difficult for the cells to grow. Hence, passage culture may be performed in which the cultivated cells are collected and moved into a new vessel to maintain the cultivation of the cells.
In the passage culture, it is necessary to separate the cells adhered to the culture vessel; the conditions of the adherence are often different depending on variations between the individual cells. Hence, according to the conditions of the adherence of the cells to the culture vessel, it is required to adjust the number of times of washing of and the amount of flow of washing of the cells before being separated, to adjust a time up to trypsin separation and to change the force of hitting and the number of times of hitting the culture vessel in order to complete the separation operation. Hence, it is necessary to accurately determine the state of floatation of the cells in the culture solution within the culture vessel and the state of the adherence. Furthermore, when it is possible to distinguish between the state of floatation of and the state of adherence of the cells contained in the culture vessel, the graft survival after the cell dissemination in the culture vessel can be roughly estimated.
Examples of the method of distinguishing between the state of floatation of the cells in the culture solution within the culture vessel and the state of the adherence, as described above, can be found in Patent documents 1 and 2. In a recognition device disclosed in Patent document 1, a stage on which a culture vessel is placed is moved to produce convection within the culture vessel, and thus physical vibrations that cause the displacement of the cells floated within the culture vessel but does not cause the displacement of the cells adhered are provided with the result that images are sensed and analyzed. In a cell separation determination method disclosed in Patent document 2, a culture vessel placed on a vibration application stage is vibrated together with the vibration application stage and two images of a culture solution at rest and after being vibrated are sensed, and are distinguished between a state of floatation of the cells and a state of adherence thereof.